Epidemiological and Entomological Evaluations after Six Years or More of Mass Drug Administration for Lymphatic Filariasis Elimination in Nigeria

Abstract

The current strategy for interrupting transmission of lymphatic filariasis (LF) is annual mass drug administration (MDA), at good coverage, for 6 or more years. We describe our programmatic experience delivering the MDA combination of ivermectin and albendazole in Plateau and Nasarawa states in central Nigeria, where LF is caused by anopheline transmitted Wuchereria bancrofti. Baseline LF mapping using rapid blood antigen detection tests showed mean local government area (LGA) prevalence of 23% (range 4–62%). MDA was launched in 2000 and by 2003 had been scaled up to full geographic coverage in all 30 LGAs in the two states; over 26 million cumulative directly observed treatments were provided by community drug distributors over the intervention period. Reported treatment coverage for each round was ≥85% of the treatment eligible population of 3.7 million, although a population-based coverage survey in 2003 showed lower coverage (72.2%; 95% CI 65.5–79.0%). To determine impact on transmission, we monitored three LF infection parameters (microfilaremia, antigenemia, and mosquito infection) in 10 sentinel villages (SVs) serially. The last monitoring was done in 2009, when SVs had been treated for 7–10 years. Microfilaremia in 2009 decreased by 83% from baseline (from 4.9% to 0.8%); antigenemia by 67% (from 21.6% to 7.2%); mosquito infection rate (all larval stages) by 86% (from 3.1% to 0.4%); and mosquito infectivity rate (L3 stages) by 76% (from 1.3% to 0.3%). All changes were statistically significant. Results suggest that LF transmission has been interrupted in 5 of the 10 SVs, based on 2009 finding of microfilaremia ≥1% and/or L3 stages in mosquitoes. Four of the five SVs where transmission persists had baseline antigenemia prevalence of >25%. Longer or additional interventions (e.g., more frequent MDA treatments, insecticidal bed nets) should be considered for ‘hot spots’ where transmission is ongoing.

The Impact of Six Annual Rounds of Mass Drug Administration on Wuchereria bancrofti Infections in Humans and in Mosquitoes in Mali

“…Consistent with the data from other studies, [9][10][11] six rounds of MDA with albendazole and ivermectin were extremely effective in reducing the prevalence of W. bancrofti microfilaremia in residents of a highly endemic area of Mali. Although testing for microfilaremia was limited to 53.02% (604/1139) of the total population eligible for MDA in the six villages, it is unlikely that the infection rate in the remaining population was substantially higher than that in the tested subjects.…”

“…[9][10][11] To evaluate the effect of ALB/IVER on W. bancrofti transmission in varied epidemiologic settings in Africa, a multi-country study was initiated in 2001 in Mali and Ghana (West Africa) and Kenya (East Africa). Regular assessments of prevalence in the human population (circulating filarial antigen and microfilarial levels), and in the Anopheles vector population (annual transmission potential [ATP]) were conducted prior to and during six annual MDA using ALB/IVER.…”

Community-Wide Distribution of Long-Lasting Insecticidal Nets Can Halt Transmission of Lymphatic Filariasis in Southeastern Nigeria

“…Indoor-resting mosquitoes were collected as described. 23,24 The dead and dying mosquitoes that were collected were immediately placed in Petri dishes containing moist tissue, and the dishes were kept in coolers with wet towels until dissections were performed, always on the day of collection and usually in the same village. Each mosquito was identified as An.…”

Evidence for Stopping Mass Drug Administration for Lymphatic Filariasis in Some, But Not All Local Government Areas of Plateau and Nasarawa States, Nigeria

“…6 Baseline LF mapping using rapid blood antigen detection tests showed mean local government area (LGA) prevalence of 23% (range 4-62%) among persons 15 years of age and older in 70 randomly selected sites in the two states. 7,8 Since 2000, health education plus MDA using 150 μg/kg of ivermectin (Mectizan ; donated by Merck & Co., Inc., Whitehouse Station, NJ) and 400 mg of albendazole (donated by GlaxoSmithKline, Brentford, Middlesex, UK) have been implemented annually according to WHO guidelines to eliminate LF transmission, using each LGA as an independent MDA implementation unit. A phased LGA scale-up to implementing MDA was adopted in the two states as capacity of the program increased and by 2003 all 30 LGAs within the states were under MDA interventions.…”

“…A phased LGA scale-up to implementing MDA was adopted in the two states as capacity of the program increased and by 2003 all 30 LGAs within the states were under MDA interventions. 7 Reported treatment coverage for each round was 85%, with over 3.1 million persons being treated annually of the treatment eligible population of 3.7 million. A population-based coverage survey in 2003 estimated coverage of 72.2% of the eligible population (95% confidence interval [CI] = 65.5-79.0%) for the overall two-state area.…”